Method of manufacturing high compression automotive distillate



C. J. PRATT Filed June 14, 1928 METHOD OF MANUFACTURING HIGH COMPRESSIONAUTOMOTIVE DISTILLATE June 16, 1931.

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Patented June 16, 1931 ALTENT OFFICE CLIFTON JOHN PRATT, OF ST. LOUIS,MISSOURI, ASSIGNOR TO THE AUTOMOTIVE DIS- TILLATE CORPORATION, OFINDEPENDENCE, KANSAS, A CORPORATION OF KANSAS METHOD OF MANUFACTURINGHIGH COMPRESSION AUTOMOTIVE DISTILLATE Application filed June 14,

This invention relates to a process of, and apparatus for distillingoils and with re-. gard to certain more specific features to the methodof and apparatus for improvedly converting crude petroleum oil into highcompression automotive distillate.

Among the several objects of the invention may be noted the provision ofimproved means for carrying on a plurality of cracking processes on agiven oil'in such manner that coking in the furnace tubes is eliminatedand a better product produced but at the same time carrying on one ofsaid cracking processes directly in the tubes of a heating furnace,whereby the requirements for an expansion chamber is eliminatedptheprovision of means for effecting an improved blend of the products dueto said cracking processes; the provision of apparatus for thepurposeset forth having a minimum number of elements and requiring theminimum amount of heat; and the provision of means of the classdescribed in which accurate control may be had with less difliculty.Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly comprsies the elements and combinations ofelements, steps and sequence of steps, features of construction, andarrangements of parts which will be exemplified in the structurehereinafter described, and the scope of the ap-plicatlon of which willbe indicated in the following claims.

In the accompanying drawing, in which is illustrated one of variouspossible embodiments of the invention, the figure illustratesdiagrammatically the relationship between the elements of the system.

1 Similar reference characters indicate corresponding parts throughoutthe single view of the drawing.

Referring now more particularly to the drawing, numeral 1 indicates asupply tank for crude oil, numeral 3 indicates a residuum tank, numeral5 a tank for precracked or recycled stock and numeral 7 a gasoline tank.It isto be understood that the term gasoline \valves 39the heatexchanger 35 can be bypassed by the hot residuum passing toward 1928.Serial No. 285,407.

sion automotive distillate obtained by the present process.

Numerals 9 and 11 indicate cooling boxes for the purpose of coolingmaterials passed to the tanks 3 and 5 respectively and 13 is a condenserbox for material passing to tank 7. Numerals 15 and 17 indicate outletsfor tanks land 5 respectivelywhich outlets pass to pumps 19 and 21respectively.

The crude oil pump 19 has an outlet 23 from which branches one line 25to a furnace connection 27 and another line 29 which passes to anevaporating chamber 31 of a bubble tower 33. The line 29 passes througha heat exchanger 35 the latter being heated by the hot residuum whichpasses from said evaporating chamber 31 to residuum tank 3, providedthat valve 37 is closed and valves 39 are open. By opening valve 37 andclosing the tank 3. Valves 41 and 43 permit of control of lines 25 and29 in such a way that the pump 7 19 may be caused to pump through eitherof the lines 25 or 29 separatel or through both in any desiredproportion, ependingupon the relative valve openings. Suitable metersand gauges are used in connection with the pumps.

The pump 21 is equipped withan outlet line 45, also leading to saidfurnace connec'- tion 27 by wa offpreheating or reflux coils 47 and 49.Viilve's 51 and 53 on each side of the furnace connection 27 permit ofsuch control that either of the pumps may be cut into or out of actionfor pumping liquid into the cracking furnace F through the connection27. Or said valves 51, 53 may be set to permit passage to the furnacefrom both pumps 19 and 21. i

The single cracking furnace. F is equipped with heating tubes 55 whichare in communication with the connection 27 and in communication' withan outlet line 57 leading to the evaporating chamber 31 of the bubbletower 33. A suitable burner 59 is used to heat" the furnace.

It will be noted that one preheating or reflux coil 49 is in theevaporating chamber 31, and the other preheating or reflux coil 47 isherein. refers to the improved high compresin the fractionating ordephlegmating chamber 61, of the bubble tower 33, the chamber 61 beingin communication with the chamber 31 by way of the stand pipe 63. Avapor outlet line is provided from the top of the fractionating chamberand passes to the gasoline tank 7 by way of condenser box 13.

Suitable pyrometers P are used for checking temperatures throughout thesystem.

' The operation may be divided into two stages, namely, (A) startingoperation, and (B) continuous operation.

(A) To start, valves 43, 39 and 53 are shut, while valves 41, 37 and 51are open. Pump 19 is started but pump 21 is not. The burner 59 isoperated at a relatively low rate. Hence the pump 19 withdraws crude oilfrom the tank 1 and delivers it by way of valve 41, line 25, valve 51,connection 27, tubes 55 and line 57 to the evaporating chamber 31.Inasmuch as crude oil has a great tendency to coke in the furnace tubeswhen too high a heat is used, the heat of the furnace is kept down sothat coking of the crude oil is prevented in the tubes 55. Thetemperature at this stage of the operation in line 57 is of the order of800 degrees F: but this may be somewhat varied with the particular crudestock being used. The point is that the temperature should understarting conditions be kept down so that coking of the crude oil in thetubes 55 is prevented.

Under the starting conditions recited above the rate of distillation islow. Hot

residuum and unevaporated crudes collect in the chamber 31 and flow tothe residuum tank 3 through valve 37. Somevapors pass into thefractionating chamber 61, where fractionating takes place, at least tothe extent of forming a liquid level 67 of intermediate fraction orrecycling stock which flows into the tank 5.

(B) After a period of operation such as above described, the pump 21 isstarted for continuous operation and the crude oil pump 19 is permittedto continue running. However, all valves are reversed in position sothat valves 43,39 and 53 are open, while valves 41, 37 and 51 areclosed. This results in the, pump 21 delivering recycling stock from thebulk supply in the tank 5 through line 45 (including preheating coils 47and 49) through the furnace connection 27, furnace coils 55 and line 57to the evaporating chamber 31. Thus it will be seen that instead ofcrude stock being pumped through the cracking furnace F, that the clearand beter quality of intermediate, recycling stock from tank 5 is pumpedthrough said furnace. The recyclingstock better resists coking at highertem eratures than the crude stock, so that the urner 59 is now causedtoincrease the furnace temperature. During continuous operation theter'npearture in line 57 is of the order of 1250 degrees F., dependingupon 65 the particular oil being treated, It will be seen that thefurnace temperature is some v four to five hundred degrees higher undercontinuous operating conditions as compared with starting operatingconditions. The clear recycling stock enters the furnace at atemperature of the order of 550 degrees 13]., due to the action of thepreheating coils 4 ,49.

It is to be understood that the change over from operation A to B may bemade graduallyby' slowly opening valves 43, 39 and 53 and proportionallyslowly closing valves 41, 37 and 51. At the same time the temperature ofthe furnace gradually increases.

Under ultimate continuous operating conditions, the pump 19 pumps all ofthe crude oil through line 29 and heat exchanger 35 to the evaporatingchamber 31 where it meets the high temperature cracked vapors from thecracking furnace. The residuum from chamber 31 flows through the heatexchanger 35 to preheat the crude oil and in efi'ect said heat exchangertakes the place of the furnace F in regard to heating the crude oil. Thetemperature of the oil due to the action of the preheater is not'such asto cause coking but it does effect an incipient distillation.

Under the continuous operating conditions full distillation is had andthe vapors from both the crude and recycling stockspass into thefractionating chamber 61 and are separated therein to provide bothintermediate fractions for further carrying on the recycling process andalso to provide light vapors which pass out through line 65 to thecondenser 13, and are condensed to distillate or gasoline which passesto the tank 7. Hence with one furnace the advantages are had ofsegregating the means for heating crude stock and recycled stock andalso the advantage of obtaining a blending action in the bubble tower33. The blending can be controlled by controlling temperatures andpressures throughout the system, that is, Within the limits for properheating of the oil in View of this invention.

One of the features of the present invention I comprises the operationof the system such that the recycled, intermediate stock passing throughthe coils 55 will reach a cracking temperature in said tubes, the tubesbeing long enough to permit this action. Hence,

stock from the cracking furnace F. In the present invention, theintimate contacting is achieved by maintaining a liqud level of thepreheated crude stock in the vaporizing chamber 31, and introducing thesaid superheated cracked vapors below this liquid level. The bubbletower 33 also provides a fractionating or dephlegmating chamber 61. Saidbubble in the cracking tower 33 is not maintained at high pressures, buton the contrary is maintained atsubstantially atmospheric pressure.

It will be seen that the recycled stock collecting in the bottom of thefractionating chamber 61 comprises an intermediate fraction, fromwhichthe residuums and higher boiling-point coke-forming constituentshave already'been removed. This stock has already been subjected'to atleast one crackin operation (in the evaporating chamber 31 and may,therefore, be termed a precracked stock,

By using the recracked or recycled stock Furnace F for high temperatureoperation, the formation of carbon is minimized. The'small amount offree carbon that may be produced in tubes is carried forwardly in thetubes by the velocity of the vapors due to cracking in the tubes, saidcarbon being held in suspension be: cause of the turbulence had at bendsand the like. Thus instead of carbon deposits building up in tubes 55,the carbon is carried over to the bubble tower.

Some carbon is also directly formed in the bubble tower due to thecracking action of the cracked vapors on the preheated crude oil.However, the formation and agglomeration of carbon in the bubble toweris not a serious result, inasmuch as the carbon formed is of a porousand spongy nature through which operations may be continued withoutinterruption of the plant. Even excessive deposits are easily cleanedout. Onthe other hand, if these deposits were permitted to occur in thetubes 55, much more dificulty would be had. The tubes might burn out andat best they would clog up sooner and prevent operation altogether.

In the present process the crude oil itself is cracked so as to obtainthe greatest percentage of lowest boiling point h drocarbons. This isdone by breaking up t e highest boiling point hydrocarbons in the crudeoil. In the case of the precracked or recycled stock there are producedby cracking hydrocarbons coming in the gasoline series but with aboiling point range substantially higher, so that a maximum percentageof higher boiling point hydrocarbons is had. By blending thesehydrocarbons from both the crudes and the cracked recycled stock in thebubble tower the advantages of both results are bad in the finalcondensed product passing to tank 7.

Under starting conditions the head pressure for pump 19 is about fivepounds gauge. Under running conditions it is about two pounds gauge andwhenever the puinp 21 is running its head pressure is about seventyfivepounds gauge. It is to be noted that these pressures are for the purposeof overcoming frictional resistance in the piping, coils, and the like,only, and do not constitute superimposed pressures requiring expansionvalves at subsequent points in the apparatus. It is intended thatpressure and temperature be so controlled within the requirements forthe improved operations set out that the pressure in the bubble tower 33will remain at about that of the atmosphere, that is, zero pounds gauge.

lln view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

I claim:

( 1. The process of treating hydrocarbons which comprises preheatingsaid hydrocarvapors to form recycling hydrocarbons, sep- 7,

arately removing and cooling said recycling hydrocarbons, maintaining anindependent bulk supply of said cooled recycling hydrocarbons, wherebythe optimum treating conditions for said recycling hydrocarbons may becontinuously controlled, withdrawing recycled hydrocarbons from saidbulk supply, and substantially completely cracking said recycledhydrocarbons without dilution in the vapor phase ata temperature of theorder of 1250 F. at substantially no superimposed pressure, bringing thehot cracked vapors thus formed into contact with said preheatedhydrocarbons, and removing light cracked hydrocarbon vapors andcondensing the same.

2. The process of treating hydrocarbons which comprises preheating saidhydrocarbons, subjecting said "preheated hydrocarbons to a preliminarycracking operation at substantially atmospheric pressure by establishinga liquid level of said preheated hydrocarbons and introducing crackedhydrocarbon vapors beneath said liquid level, whereby the preheatedhydrocarbons are cracked and mixed vapors and liquid residuums areformed,-removing said liquid residuums, partially condensing said mixedvapors removing and cooling said recycling hydrocarbons by indirect heatexchange, maintain- I ing an independent bulk supply of said cooledrecycling hydrocarbons, whereby the 0 timum treating conditions for saidrecyc mg hydrocarbons may be continuously controlled, withdrawingrecycled h drocarbons from said bulk supply, preheatmg the withdrawnrecycling hydrocarbons by indirect heat exchange with said mixed vapors,and substantially completely cracking said recycled hydrocarbons withoutdilution in the vapor phase at a temperature of the order of 1250" F. atsubstantially no superimposed pressure,

bringing the hot cracked vapors thus formed a into contact With saidpreheated hydrocarbons, and removing light cracked hydrocarbon vaporsand condensing the same.

In testimony whereof, I have signed my name to this specification this11th day of June, 1928. V

p CLIFTON JOHN PRATT.

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